Mac Mini 2006 fresh install of Mac OS X 10.6.8 Snow Leopard

I'm having a great deal of trouble doing a fresh install on my Mac Mini

Specs as far as I know are: 1.83 GHz Core Duo (T2400) Model A1176 (EMC 2108)

It currently when starting it up has Mythbuntu installed on it (on Linux I'm guessing I'm not sure) and I want to be able to install OS X 10.6.8 Snow Leopard (I believe thats the latest version that will work with that model) so I can install an older version of Plex (it won't be connected to the Internet, just for using as a media server)

So I have tried making a bootable USB of Mountain Lion which is the earliest version OS I have on iTunes, it was successful, I thought I would try it in case it worked, but I will have to buy Snow Leopard do you think?

When I try command+R on start up the screen goes blank, then it shows a folder with a question mark and then just a faint grey stop symbol (circle with a diagonal line).

I'm hesitant to fork out the $30 something dollars for Snow Leopard download if I won't be able to even get it to boot up into that. I also tried command+alt+r. If I just boot it up normally it loads up into Mythbuntu options screen but I want to put a proper OS X and use it as a media player.

If anyone has any advice you could give I would be most grateful. My husband used to take care of all the technical stuff but he passed away last year and the kids are now hassling me to get it sorted out and we miss watching our files and music. Thanks!